1. Field of the Invention
The present invention relates generally to the implementation of a system implemented to rapidly insert a purge gas into the combustion intake of a carbureted or non-carbureted liquid or gaseous fueled engine to interrupt undesired dieseling or “run on” by rapid alteration of the air-fuel ratio away from the stoichiometric air-fuel ratio necessary to continue operation of the engine under these conditions. This concept can be readily implemented on any internal combustion power cycle mechanical system.
2. Background and Description of the Related Art
In many instances operators of carbureted engines experience continued run on after the ignition system has been turned off. Additionally, there may be instances where fuel shut-off in a diesel engine is impaired or incomplete. In those instances where engine shut-off is a safety issue, there can be danger to the operator or others and a related hazard to human health and safety. In view of the forgoing, there is a need for improved systems to assist users of internal combustion engines to quickly stop engines experiencing such post shut-off dieseling.
In the case of carbureted engines, one of the principal issues causing improper shut down of carbureted engines is engine run on due to “dieseling”, even when following the normally prescribed operator actions. Under certain conditions, such engines continue running even when the spark plugs are not firing (i.e. Ignition is OFF). The cause of the “dieseling” is due to having an adequate mixture of fuel and oxygen and an uncontrolled ignition source in the combustion chamber. Typically the ignition source should be eliminated by shutting down the spark to the spark plug. However, under certain conditions, compression of the fuel/air mixture and the temperature of the engine or fuel may produce enough heat produce an uncontrolled ignition of the fuel and, consequently, undesired run on. Operation of the engine in this mode can lead to engine damage and hazards to the engine operator or others near to or involved with the operation of the engine or other machinery powered by the engine.
The inventor of the concepts disclosed herein experienced this problem with his carbureted boat engine, which operates on regular, unleaded fuel (87 octane recommended). The problem most often would occur after operating the boat under nearly full power conditions for an extended time and then, following the recommended practices for operating the boat, placing the throttle in neutral and attempting to shut the engine off using only the ignition switch. The expectation of this ignition shut-off is the safe shutdown of the engine and reducing the risk of a turning propeller to attend to persons needing assistance to get into the boat, coming to the aid of another boater, arrival at a dock or beaching destination or other reasons that it might be desirable to cease engine operation. In a substantial number of instances, the engine would continue to run (to “diesel”) even after when the ignition system was placed in the “OFF” position. Consequently, to achieve complete engine shut down, the ignition key was placed back in the “ON” position and operate the engine at idle speed for a sufficient time to lower the engine operating temperature. Once the engine temperature was low enough, it would not “diesel” when the key was placed to “OFF” and the engine successfully shut down. The problem introduced by this mode of operation is that such timing, in many instances, was longer than the desired shutdown time and, also, depending on conditions, an indeterminate amount of time. The latter issue perhaps caused by variance in the start temperature and resulting, for some instances, in the need for multiple attempts at cool down idle times before the engine could be stopped.
Research of potential solutions for this problem included consulting with several boat shop owners and the boat engine manufacturer. This research concluded this dieseling run-on was a common problem attributed to the compression ratio in the engine and current fuel formulations used in the engine. Other contributors were determined to include the engine model, service conditions, cooling configurations, fuel type used, and other conditions that influence the development of an uncontrolled ignition source in the combustion chamber of the engine. A mechanical solution was available from the manufacturer, which addressed the problem by mechanical isolation of the air-fuel mixture flowing out of the carburetor and through the intake system to stop the run-on after engine shut off. The manufacturer's other recommendations and suggestions included altering the operating conditions that might enable dieseling by using a lower thermostat setting, using lower temperature spark plugs, or increasing ventilation to the engine compartment. Further review of boat owner web sites shows these solutions do not always solve the problem, nor were they successful in terms of acceptable results for this applicant.
The solution offered here is to introduce a purge gas to the intake combustion air scheme enabling a rapid change in the air-fuel ratio away from stoichiometric air-fuel ratio in the combustion chamber by providing a burst of a selected purge gas to the engine air intake or carburetor when the “dieseling” conditions are present. In addition, if the purge gas is obtained from a compressed gas container, the expansion of the gas will also provide a cooling effect that also helps to eliminate the ignition source. The purge gas can be any number of gas types, inert or otherwise, that are introduced to the air intake, carburetion or fuel mixture distribution systems on the engine to rapidly change the air-fuel mixture and, consequently, interrupt the engine run-on by starving the combustion process. This is an improvement over those solutions previously identified and would be preferred for the following reasons:
Many of the embodiments presented here can be implemented with simple additions or modifications to the current engine application. Thus, there is minimal cost to add to existing or new engines,
It is a reliable method that can be used to address multiple conditions such as carbon build up, bad spark plugs, and other problems that may promote engine run-on/dieseling.
It is simple to use apply and use. It can be designed for automatic or manual mechanical or electro-mechanical operation.
It requires minimal operator action and could be fully automated to operate when needed without any operator action
It is only used when necessary. In other words, if operation of the engine will not result in a dieseling problem (such as when the engine has operated at low/idle speed just prior to shutdown), the solution is not applied.
It can be safely used on any internal combustion engine or other mechanical power source of similar configuration.
It can be used in combination with other solutions if redundancy is desirable or necessary. And if, so applied, does not interfere with those other means.
Embodiments of the present invention described in the following provide further evidence of the advantages listed above. As such, features and alternate considerations that promote those advantages will be highlighted.